Trap: strategic product placement

Avoid it. Write down what you need beforehand and you won’t be tempted to veer off course. Scope out bottom shelves, too; that’s where the least expensive items are often located.

Trap: checkout tchotchkes

Merchandisers know you’re probably tired and hungry when you’re waiting to pay, which is why you’ll find small items meant to spur impulse buys, such as lip gloss and candy bars.

Avoid it. Distract yourself by texting a pal. Also, if you ask yourself what you’re truly craving (lunch?), you won’t have to fill the void with a splurge.

Trap: a myriad of mirrors

“Shoppers who check out their reflections may be prone to self-critical thoughts, leading them to buy products to fix themselves,” says Alan Guinn, managing director of the Guinn Consultancy Group, in Bristol, Tennessee.

Avoid it. If you didn’t walk in thinking you needed improvement, leave that tooth whitener on the shelf. See a mirror? Give yourself a compliment. (“Good-hair day!”)

Trap: A racetrack floor plan

Many shops are set up as a circuit that guides you past the greatest number of items, so you linger longer. Trouble is, “The more time you’re in the store, the more you’ll be apt to buy,” points out Pam Danziger, founder of Unity Marketing in Stevens, Pennsylvania.

Avoid it. Don’t wander around; go straight to what you need. And set a time limit. When shoppers exceed 30 minutes, there’s a spending bump.

Trap: mega-baskets

Many baskets and carts are supersized these days, and that’s no accident. “When you see extra space in the cart, you may wonder what you are forgetting—and then buy more,” Guinn explains.

Avoid it. Skip the cart altogether and grab a small basket or, if possible, use only your hands.

Trap: discounts, one-day-only sales and “special” offers

Markdowns lead you to believe that you are snagging a deal; limited-time offers create a false sense of urgency; buy-one-get-one-free specials encourage you to rationalize the purchases you wouldn’t otherwise make.

Avoid it. Ask, “Would I buy this if it weren’t on sale or if a freebie weren’t included?” If the answer is no, put it back and save your cash.

Trap: freebies and friendly salespeople

Interacting with store employees (perfume samples! cheese cubes!) can make you feel connected to them. “That leaves you with a sense of obligation to buy,” Yarrow says.

Avoid it. Go ahead—take the free treat, but remind yourself that you’re not responsible for helping a saleswoman make her quota. To be safe, skip unnecessary small talk, too.

Trap: artful pairings

The reason shoes are placed next to bags: When you commit to a splurge, you’re more open to buying a complementary item.

Avoid it. Tell yourself that there may be a better deal elsewhere (e.g., you’ll find cheaper batteries at Costco than by the gadgets in an electronics store).